Calibration Intervals · 5 min read
Adjusting Calibration Intervals Using As-Found History
The best calibration programs treat intervals as a hypothesis they keep testing. As-found data is the evidence that lets you tighten or relax an interval with confidence instead of guesswork.
Part of our guide to Calibration Intervals & Program Scheduling.
The feedback loop
Every calibration produces as-found data: was the instrument in tolerance when it arrived? Track that over several cycles. Instruments that consistently return well within tolerance are candidates for a longer interval; instruments found out of tolerance, or trending toward a limit, should have their intervals shortened. This is interval analysis, and it turns your calibration spend into a managed risk rather than a flat calendar cost.
Do it carefully — and record it
Extend intervals in measured steps, not leaps, and only with enough history to justify it. Document each change and its basis. An auditor seeing intervals adjusted with as-found evidence sees a mature program; intervals that only ever grow to save money, with no data, are a finding waiting to happen.
Common questions
How much history do I need before extending?
Enough to show a stable pattern — typically several consecutive in-tolerance cycles. The riskier the measurement, the more evidence you should require before lengthening the interval.